Spatial analysis and environmental drivers of small-flowered balsam (Impatiens parviflora DC.) invasion in urban forests.

Abstract

Invasive species are one of the most important threats to global biodiversity, often altering the structure of native plant communities. Impatiens parviflora DC., annual invasive plant species from Central Asia, while long-established in Europe, continues to expand its range, particularly in closed-canopy forests and riparian ecosystems. It is particularly abundant in disturbed forests. Although urban forests are under several human impacts, studies on the ecology of this widespread invasive species are scarce. Understanding the specific environmental factors, such as light availability, soil moisture, and human impact, is crucial for predicting its further spread and managing urban green infrastructure, particularly forests. We analyzed the distribution of I. parviflora in the Bogdanka River Valley (Poznań, Poland), intensively studied forest wedge across the urban-rural gradient, typical of urban forests in Central Europe. We used a systematic sampling design, comparing invaded plots with non-invaded control sites. Within a grid we established sample plots where we assessed the presence and cover of I. parviflora . We also collected data about vegetation type, cover of vegetation layers, canopy light transmittance, remotely-sensed moisture proxies (Topographic Wetness Index, distance to water, and indirect indication by vegetation indices), and landscape structure (cover and distances to river, roads, and buildings). We used these data to develop generalized linear mixed-effects models of I. parviflora presence and cover. In the study we provided a comprehensive spatial database and high-resolution distribution maps of I. parviflora distributions and cover. Preliminary analyses aim to identify whether forest type, canopy closure, or anthropogenic soil disturbance (proximity to paths) is the dominant driver of invasion intensity along the urban-rural gradient. By integrating field survey with remote sensing and GIS analyses, this study offers a scalable method for monitoring invasive species. The findings will be described in a scientific article and shared on the iNaturalist platform to support citizen science and professional conservation efforts.